/*
 * JpegSegmentReader.java
 *
 * This class written by Drew Noakes, in accordance with the Jpeg specification.
 *
 * This is public domain software - that is, you can do whatever you want
 * with it, and include it software that is licensed under the GNU or the
 * BSD license, or whatever other licence you choose, including proprietary
 * closed source licenses.  I do ask that you leave this header in tact.
 *
 * If you make modifications to this code that you think would benefit the
 * wider community, please send me a copy and I'll post it on my site.
 *
 * If you make use of this code, I'd appreciate hearing about it.
 *   drew@drewnoakes.com
 * Latest version of this software kept at
 *   http://drewnoakes.com/
 *
 * Created by dnoakes on 04-Nov-2002 00:54:00 using IntelliJ IDEA
 */
package com.drew.imaging.jpeg;

import java.io.*;

/**
 * Performs read functions of Jpeg files, returning specific file segments. TODO
 * add a findAvailableSegments() method TODO add more segment identifiers TODO
 * add a getSegmentDescription() method, returning for example 'App1 application
 * data segment, commonly containing Exif data'
 * 
 * @author Drew Noakes http://drewnoakes.com
 */
public class JpegSegmentReader {
	// Jpeg data can be sourced from either a file, byte[] or InputStream

	/** Jpeg file */
	private final File _file;
	/** Jpeg data as byte array */
	private final byte[] _data;
	/** Jpeg data as an InputStream */
	private final InputStream _stream;

	private JpegSegmentData _segmentData;

	/**
	 * Private, because this segment crashes my algorithm, and searching for it
	 * doesn't work (yet).
	 */
	public static final byte SEGMENT_SOS = (byte) 0xDA;

	/**
	 * Private, because one wouldn't search for it.
	 */
	public static final byte MARKER_EOI = (byte) 0xD9;

	/** APP0 Jpeg segment identifier -- Jfif data. */
	public static final byte SEGMENT_APP0 = (byte) 0xE0;
	/** APP1 Jpeg segment identifier -- where Exif data is kept. */
	public static final byte SEGMENT_APP1 = (byte) 0xE1;
	/** APP2 Jpeg segment identifier. */
	public static final byte SEGMENT_APP2 = (byte) 0xE2;
	/** APP3 Jpeg segment identifier. */
	public static final byte SEGMENT_APP3 = (byte) 0xE3;
	/** APP4 Jpeg segment identifier. */
	public static final byte SEGMENT_APP4 = (byte) 0xE4;
	/** APP5 Jpeg segment identifier. */
	public static final byte SEGMENT_APP5 = (byte) 0xE5;
	/** APP6 Jpeg segment identifier. */
	public static final byte SEGMENT_APP6 = (byte) 0xE6;
	/** APP7 Jpeg segment identifier. */
	public static final byte SEGMENT_APP7 = (byte) 0xE7;
	/** APP8 Jpeg segment identifier. */
	public static final byte SEGMENT_APP8 = (byte) 0xE8;
	/** APP9 Jpeg segment identifier. */
	public static final byte SEGMENT_APP9 = (byte) 0xE9;
	/** APPA Jpeg segment identifier -- can hold Unicode comments. */
	public static final byte SEGMENT_APPA = (byte) 0xEA;
	/** APPB Jpeg segment identifier. */
	public static final byte SEGMENT_APPB = (byte) 0xEB;
	/** APPC Jpeg segment identifier. */
	public static final byte SEGMENT_APPC = (byte) 0xEC;
	/** APPD Jpeg segment identifier -- IPTC data in here. */
	public static final byte SEGMENT_APPD = (byte) 0xED;
	/** APPE Jpeg segment identifier. */
	public static final byte SEGMENT_APPE = (byte) 0xEE;
	/** APPF Jpeg segment identifier. */
	public static final byte SEGMENT_APPF = (byte) 0xEF;
	/** Start Of Image segment identifier. */
	public static final byte SEGMENT_SOI = (byte) 0xD8;
	/** Define Quantization Table segment identifier. */
	public static final byte SEGMENT_DQT = (byte) 0xDB;
	/** Define Huffman Table segment identifier. */
	public static final byte SEGMENT_DHT = (byte) 0xC4;
	/** Start-of-Frame Zero segment identifier. */
	public static final byte SEGMENT_SOF0 = (byte) 0xC0;
	/** Jpeg comment segment identifier. */
	public static final byte SEGMENT_COM = (byte) 0xFE;

	/**
	 * Creates a JpegSegmentReader for a specific file.
	 * 
	 * @param file
	 *            the Jpeg file to read segments from
	 */
	public JpegSegmentReader(File file) throws JpegProcessingException {
		_file = file;
		_data = null;
		_stream = null;

		readSegments();
	}

	/**
	 * Creates a JpegSegmentReader for a byte array.
	 * 
	 * @param fileContents
	 *            the byte array containing Jpeg data
	 */
	public JpegSegmentReader(byte[] fileContents)
			throws JpegProcessingException {
		_file = null;
		_data = fileContents;
		_stream = null;

		readSegments();
	}

	public JpegSegmentReader(InputStream in) throws JpegProcessingException {
		_stream = in;
		_file = null;
		_data = null;

		readSegments();
	}

	public JpegSegmentReader(JpegSegmentData segmentData) {
		_file = null;
		_data = null;
		_stream = null;

		_segmentData = segmentData;
	}

	/**
	 * Reads the first instance of a given Jpeg segment, returning the contents
	 * as a byte array.
	 * 
	 * @param segmentMarker
	 *            the byte identifier for the desired segment
	 * @return the byte array if found, else null
	 * @throws JpegProcessingException
	 *             for any problems processing the Jpeg data, including inner
	 *             IOExceptions
	 */
	public byte[] readSegment(byte segmentMarker)
			throws JpegProcessingException {
		return readSegment(segmentMarker, 0);
	}

	/**
	 * Reads the first instance of a given Jpeg segment, returning the contents
	 * as a byte array.
	 * 
	 * @param segmentMarker
	 *            the byte identifier for the desired segment
	 * @param occurrence
	 *            the occurrence of the specified segment within the jpeg file
	 * @return the byte array if found, else null
	 */
	public byte[] readSegment(byte segmentMarker, int occurrence) {
		return _segmentData.getSegment(segmentMarker, occurrence);
	}

	public final int getSegmentCount(byte segmentMarker) {
		return _segmentData.getSegmentCount(segmentMarker);
	}

	public final JpegSegmentData getSegmentData() {
		return _segmentData;
	}

	private void readSegments() throws JpegProcessingException {
		_segmentData = new JpegSegmentData();

		BufferedInputStream inStream = getJpegInputStream();
		try {
			int offset = 0;
			// first two bytes should be jpeg magic number
			if (!isValidJpegHeaderBytes(inStream)) {
				throw new JpegProcessingException("not a jpeg file");
			}
			offset += 2;
			do {
				// next byte is 0xFF
				byte segmentIdentifier = (byte) (inStream.read() & 0xFF);
				if ((segmentIdentifier & 0xFF) != 0xFF) {
					throw new JpegProcessingException(
							"expected jpeg segment start identifier 0xFF at offset "
									+ offset
									+ ", not 0x"
									+ Integer
											.toHexString(segmentIdentifier & 0xFF));
				}
				offset++;
				// next byte is <segment-marker>
				byte thisSegmentMarker = (byte) (inStream.read() & 0xFF);
				//System.out.println(thisSegmentMarker);
				offset++;
				if ((thisSegmentMarker & 0xFF) == (SEGMENT_SOS & 0xFF)) {
					// The 'Start-Of-Scan' segment's length doesn't include the
					// image data, instead would
					// have to search for the two bytes: 0xFF 0xD9 (EOI).
					// It comes last so simply return at this point
					// _segmentData.addSegment(thisSegmentMarker, segmentBytes);
					//System.out.println("CUCU: " + inStream.available());
					byte[] picture = new byte[inStream.available()];
					inStream.read(picture, 0, inStream.available());
					_segmentData.addSegment(thisSegmentMarker, picture);
					return;
				} else {
					byte[] segmentLengthBytes = new byte[2];
					inStream.read(segmentLengthBytes, 0, 2);
					offset += 2;
					int segmentLength = ((segmentLengthBytes[0] << 8) & 0xFF00)
							| (segmentLengthBytes[1] & 0xFF);
					// segment length includes size bytes, so subtract two
					segmentLength -= 2;
					if (segmentLength > inStream.available())
						throw new JpegProcessingException(
								"segment size would extend beyond file stream length");
					else if (segmentLength < 0)
						throw new JpegProcessingException(
								"segment size would be less than zero");
					byte[] segmentBytes = new byte[segmentLength];
					inStream.read(segmentBytes, 0, segmentLength);
					offset += segmentLength;

					if ((thisSegmentMarker & 0xFF) == (MARKER_EOI & 0xFF)) {
						System.out.println("EOI");
						// the 'End-Of-Image' segment -- this should never be
						// found
						// in this fashion
						return;
					} else {
						_segmentData
								.addSegment(thisSegmentMarker, segmentBytes);
					}
				}
				// didn't find the one we're looking for, loop through to the
				// next segment
			} while (true);
		} catch (IOException ioe) {
			// throw new JpegProcessingException("IOException processing Jpeg
			// file", ioe);
			throw new JpegProcessingException(
					"IOException processing Jpeg file: " + ioe.getMessage(),
					ioe);
		} finally {
			try {
				if (inStream != null) {
					inStream.close();
				}
			} catch (IOException ioe) {
				// throw new JpegProcessingException("IOException processing
				// Jpeg file", ioe);
				throw new JpegProcessingException(
						"IOException processing Jpeg file: " + ioe.getMessage(),
						ioe);
			}
		}
	}

	/**
	 * Private helper method to create a BufferedInputStream of Jpeg data from
	 * whichever data source was specified upon construction of this instance.
	 * 
	 * @return a a BufferedInputStream of Jpeg data
	 * @throws JpegProcessingException
	 *             for any problems obtaining the stream
	 */
	private BufferedInputStream getJpegInputStream()
			throws JpegProcessingException {
		if (_stream != null) {
			if (_stream instanceof BufferedInputStream) {
				return (BufferedInputStream) _stream;
			} else {
				return new BufferedInputStream(_stream);
			}
		}
		InputStream inputStream;
		if (_data == null) {
			try {
				inputStream = new FileInputStream(_file);
			} catch (FileNotFoundException e) {
				throw new JpegProcessingException("Jpeg file does not exist", e);
			}
		} else {
			inputStream = new ByteArrayInputStream(_data);
		}
		return new BufferedInputStream(inputStream);
	}

	/**
	 * Helper method that validates the Jpeg file's magic number.
	 * 
	 * @param fileStream
	 *            the InputStream to read bytes from, which must be positioned
	 *            at its start (i.e. no bytes read yet)
	 * @return true if the magic number is Jpeg (0xFFD8)
	 * @throws IOException
	 *             for any problem in reading the file
	 */
	private boolean isValidJpegHeaderBytes(InputStream fileStream)
			throws IOException {
		byte[] header = new byte[2];
		fileStream.read(header, 0, 2);
		return (header[0] & 0xFF) == 0xFF && (header[1] & 0xFF) == 0xD8;
	}
}